1. Field of the Invention
This invention pertains to an expander for forming a continuous fluid-tight joint between a heat exchanger and a support plate in a single operation of the expander.
2. Background
A heat exchanger typically has a plurality of heat exchanger units or section, a burner inlet opening and a flue gas outlet opening. A partition plate, typically part of the furnace housing, has openings corresponding to, and aligned with the burner and flue gas openings in the heat exchanger and one or more of the heat exchanger parts are joined to the partition plate by an assembly means. This assembly means must create a fluid-tight seal between the peripheral edges surrounding the partition plate openings and the peripheral edges of the burner inlet and flue gas outlet openings in the heat exchanger unit.
In U.S. Pat. No. 3,940,837 to John M. Wiese and assigned to the assignee of the present invention, a heat exchanger part is formed of opposed clamshell sections having one opening defined by a peripheral flange that is folded over against the surface of the plate adjacent the opening to secure the heat exchanger to the plate.
Expanders for joining a heat exchanger to a partition plate are disclosed in Hoeffken U.S. Pat. Nos. 4,538,338, 4,663,837 and 4,649,894, all assigned to the assignee of this invention. The high volume production requirement for heat exchanger and plate assemblies of the type described herein and in the Wiese and Hoeffken patents has created a need for a more effective and less expensive apparatus and method for assembling a clamshell type heat exchanger to a partition plate. In addition, apparatus must produce a joint that is leakproof, must accommodate variations in metal thicknesses, must function even though there be deformation in the metal, and must be efficient.
Although the expanders of the Hoeffken patents provided an effective means for securing a heat exchange unit to a plate member, these expanders require at least two pressing or bending steps. Moreover, the second bending step typically must be performed with a second expander having different jaw segments or different orientations of jaw segments. As noted in the Summary of the Invention of the '837 and '338 patents, with the expanders of those patents, "[T]he initial pressing operation is followed by insertion of a second expander apparatus to fully deform or fold portions of the flange which were not forcibly engaged by the jaws of the first apparatus." These auxiliary steps have been necessitated because voids naturally develop between the jaw segments of the expander as they are moved radially outward during the bending step. As a result, a single bending step has been found to leave portions of the wall surface at the joint displaced from the rim of the opening, and so the seal formed by the first bending step is incomplete.
Thus, to ensure a leakproof seal, after the initial bending step, a second expander is inserted into the opening in the plate and engaged with the flange to fully crimp or fold the flange in the noted spaced apart areas. The second expander has a set of jaws of a pattern different from that of the first expander, such that the jaws overlap the spaced apart flange areas which were not folded tight against the shoulder of the rim by the first expander. Accordingly, in the method utilizing the apparatus of the Hoeffken patents, jaw segments act directly on all portions of the wall surface. Portions not contacted by jaw segments during the first bending step are contacted by jaw segments during a second bending step. As a result, the procedures of the Hoeffken patents, although superior to the methods of other prior art, still are more cumbersome and time-consuming than desired.
SUMMARY OF THE INVENTION
The present invention provides an improved apparatus for manufacturing a heat exchanger and partition plate for gas fired hot air furnace structures wherein in a single crimping operation a substantially rigid joint is formed between one or more openings in a clamshell type heat exchanger and a partition plate.
In accordance with one aspect of the present invention an expander will form a pressed joint between a heat exchanger and a so-called partition plate or pouch plate wherein a peripheral flange formed about an opening in the plate is inserted into a corresponding opening in the heat exchanger and deformed or folded outwardly into engagement with the inner wall surface of a shoulder formed around the opening in the heat exchanger. In accordance with the invention the joint is formed around the opening by a multiple jaw press or expander apparatus which is inserted through the opening in the plate and the heat exchanger, followed by expansion of the jaws to carry out the folding or deforming process, and then retraction of the jaws to permit removal of the apparatus. The number of jaws of the apparatus is such that this single expander operation creates a substantially leakproof seal.
In accordance with another aspect of the present invention a substantially rigid pressed joint is formed between a plate member and a heat exchanger member at cooperating openings in both members by deforming a peripheral flange on the plate member into forcible engagement with the inner wall surface of a shoulder formed around the opening of the heat exchanger and wherein an axial movement of flange deforming jaws is carried out to assure that a leakproof joint is formed regardless of variations in metal thickness and other dimensional variations of the cooperating plate and heat exchanger parts. In this regard, the present invention also provides an improved apparatus for forming a rigid pressed joint between a heat exchanger and plate assembly. The expander or joint forming apparatus is adapted to be inserted through an opening in the plate member into the interior of the heat exchanger unit wherein a plurality of jaws are moved radially outward and then axially to forcibly engage and fold a seamless flange radially outward and into forcible engagement with a rim formed on the heat exchanger. The jaws are then retracted axially and radially to permit removal of the apparatus from the opening. The number of jaws of the apparatus is such that this single expander operation creates a substantially leakproof seal.
In accordance with still a further aspect of the present invention a pressed joint is formed at an opening in cooperating heat exchanger and supporting plate parts wherein a fold or deforming operation is carried out by jaws having die surfaces which curl the end of the flange of the partition plate to form a superior rigid pressed joint which will remain tight under substantial thermal stress imposed thereon in the operating environment of a gas fired hot air furnace.
Those skilled in the art of furnace heat exchanger assemblies including manufacturing methods and apparatus therefor will appreciate the above-noted features of the present invention as well as the improved manufacturing method together with additional superior aspects of the invention upon reading the detailed description which follows in conjunction with the drawings.